Problema Solution
A box is filled with 12 green cards,5 red cards, and 3 brown cards. A card is chosen at random from the box. What is the probability that it is a green or a brown card?
Answer provided by our tutors
Using the fact that P(not a red card) = P(a green card OR a brown card) we have:
P(a green card OR a brown card) = 1 - P(red card)
P(a green card OR a brown card) = 1 - (5/(12+5+3))
P(a green card OR a brown card) = 1 - 5/20
P(a green card OR a brown card) = 15/20
P(a green card OR a brown card) = 3/4
Another way to find the probability is by using the fact that:
P(a green card OR a brown card) = P(green card) + P(brown card)
P(a green card OR a brown card) = 12/(12 + 5 + 3) + 3/(12 + 5 + 3)
P(a green card OR a brown card) = 12/20 + 3/20
P(a green card OR a brown card) = 15/20
P(a green card OR a brown card) = 3/4